Assessing the risks of recycling urban stormwater for potable supply via an aquifer

Urbanisation and the subsequent increase in impervious land use generate increased urban stormwater which can be recycled viamanaged aquifer recharge (MAR) to supplement more traditional surface or ground water supplies. This paper compares the quality of stormwater from two urban catchments in South Australia to assess the risks, in accordance with the Australian Guidelines for Water Recycling, of recycling stormwater via a limestone aquifer for potable water use. In the regional city of Mount Gambier, stormwater MARin a karstic aquifer has been used to supplement the city\u27s drinking water supply for over 100 years. The source water was generally high quality with some instances of turbidity, iron and lead exceeding the Australian Drinking Water Guidelines (ADWG). Effort wasmade to constrain the estimate of minimum residence time within the karstic aquifer to at least two years for evaluation of the potential for passive treatment of trace organic chemicals in this system. In the second example, a purpose built MAR site in Parafield, a northern suburb of Adelaide, has been designed and operated asa full scale trial to determine if wetland treated urban stormwater can be recovered at a standard which meets the ADWG. Based on the analysis undertaken, the source water was generally of high quality with occasional instances of levels of iron and microbial indicators in excess of the ADWG. After a mean residence time in the aquifer of 240 days, recovered water qualitymet the ADWGwith the exception of iron. However, given the uncertainty in pathogen concentrations in the treated stormwater post-recovery from the aquifer, disinfection and aeration for iron removal would be necessary to ensure that the ADWG were met if the water was to be utilised for potable water supply

Environmental monitoring of selected pesticides and organic chemicals in urban stormwater recycling systems using passive sampling techniques

Water recycling via aquifers has become a valuable tool to augment urban water supplies in many countries. This study reports the first use of passive samplers for monitoring of organic micropollutants in Managed Aquifer Recharge (MAR). Five different configurations of passive samplers were deployed in a stormwater treatment wetland, groundwater monitoring wells and a recovery tank to capture a range of polar and non-polar micropollutants present in the system. The passive samplers were analysed for a suite of pesticides, polycyclic aromatic hydrocarbons (PAHs) and other chemicals. As a result, 17 pesticides and pesticide degradation products, 5 PAHs and 8 other organic chemicals including flame retardants and fragrances were detected in urban stormwater recharging Aquifer Storage and Recovery (ASR) and an Aquifer Storage Transfer and Recovery (ASTR) system. Of the pesticides detected, diuron, metolachlor and chlorpyrifos were generally detected at the highest concentrations in one or more passive samplers, whereas chlorpyrifos, diuron, metolachlor, simazine, galaxolide and triallate were detected in multiple samplers. Fluorene was the PAH detected at the highest concentration and the flame retardant Tris(1-chloro-2-propyl) phosphate was the chemical detected in the greatest abundance at all sites. The passive samplers showed different efficiencies for capture of micropollutants with the Empore disc samplers giving the most reliable results. The results indicate generally low levels of organic micropollutants in the stormwater, as the contaminants detected were present at very low ng/L levels, generally two to four orders of magnitude below the drinking water guidelines (NHMRC, 2011). The efficiency of attenuation of these organic micropollutants during MAR was difficult to determine due to variations in the source water concentrations. Comparisons were made between different samplers, to give a field-based calibration where existing lab-based calibrations were unavailable

Assessing the Impact of Recycled Water Quality and Clogging on Infiltration Rates at A Pioneering Soil Aquifer Treatment (SAT) Site in Alice Springs, Northern Territory (NT), Australia

Infiltration techniques for managed aquifer recharge (MAR), such as soil aquifer treatment (SAT) can facilitate low-cost water recycling and supplement groundwater resources. However there are still challenges in sustaining adequate infiltration rates in the presence of lower permeability sediments, especially when wastewater containing suspended solids and nutrients is used to recharge the aquifer. To gain a better insight into reductions in infiltration rates during MAR, a field investigation was carried out via soil aquifer treatment (SAT) using recharge basins located within a mixture of fine and coarse grained riverine deposits in Alice Springs, Northern Territory, Australia. A total of 2.6 Mm3 was delivered via five SAT basins over six years; this evaluation focused on three years of operation (2011–2014), recharging 1.5 Mm3 treated wastewater via an expanded recharge area of approximately 38,400 m2. Average infiltration rates per basin varied from 0.1 to 1 m/day due to heterogeneous soil characteristics and variability in recharge water quality. A treatment upgrade to include sand filtration and UV disinfection (in 2013) prior to recharge improved the average infiltration rate per basin by 40% to 100%

Arsenic mobility and impact on recovered water quality during aquifer storage and recovery using reclaimed water in a carbonate aquifer

International audienceArsenic release from aquifers can be a major issue for aquifer storage and recovery (ASR) schemes and understanding the processes that release and attenuate As during ASR is the first step towards managing this issue. This study utilised the first and fourth cycles of a full scale field trial to examine the fate of As within the injectant plume during all stages of the ASR cycle, and the resultant water quality. The average recovered As concentration was greater than the source concentration; by 0.19 μmol/L (14 μg As/L) in cycle 1 and by 0.34 μmol/L (25 μg As/L) in cycle 4, indicating that As was being released from the aquifer sediments during ASR and the extent of As mobilisation did not decline with subsequent cycles. In the injection phase, As mobilisation due to oxidation of reduced minerals was limited to an oxic zone in close proximity to the ASR well, while desorption from Fe oxyhydroxide or oxide surfaces by injected P occurred further in the near well zone (0–4 m from the ASR well). With further aquifer passage during injection and greater availability of sorption sites there was evidence of attenuation via adsorption to Fe oxyhydroxides which reduced concentrations on the outer fringes of the injectant plume. During the period of aquifer storage, microbial activity resulting from the injection of organic matter resulted in increased As mobility due to reductive Fe oxyhydroxide dissolution and the subsequent loss of sorption sites and partial reduction of As(V) to the more mobile As(III). A reduced zone directly around the ASR well produced the greatest As concentration and illustrated the importance of Fe oxyhydroxides for controlling As concentrations. Given the small spatial extent of this zone, this process had little effect on the overall recovered water quality